The web server has been replaced.
The old web server ran under CentOS 6.7 Linux which had become quite outdated. CentOS provides no reliable method of doing a live upgrade from one major release to the next.
The new server runs under Ubuntu 15.10 which is current. Ubuntu provides a method of doing live upgrades and in fact I have upgraded from
12.04 -> 12.10 -> 14.04 -> 14.10 -> 15.04 -> 15.10, and while there were occasional minor issues, like Nvidia drivers being incompatible with the new kernel, all in all these upgrades were successful.
This resolved the problems with incompatible php modules and now ownCloud is fully functional.